That is a big difference between the US and British military systems. The US has always been more humanitarian to it's troops. Not one man gets left behind.
In the British view injuring a man is better than killing them because by injuring a man you take up more of the resources of the enemy. When fighting an enemy like America, Britain would be aiming to injuring more than killing. By injuring a man it would take several other guns from the battlefield, those guns who are trying to help the injured man.